The prior art includes PAGEIN/PAGEOUT instructions disclosed and claimed in U.S. Pat. No. 4,476,524 in which a first embodiment discloses a synchronous means for controlling a page transfer between a system main storage (MS) and a physically-separate extended or expanded storage (ES). A second embodiment uses the IBM S/360 Start Input Output (SIO) instruction to invoke an I/O channel program containing one or more PAGEIN/PAGEOUT channel command words (CCWs) to control an asynchronous page transfer between the main storage and the expanded store. The asynchronous embodiment uses an I/O channel-end interruption at the end of the channel program execution to signal the end of each group of page transfers. This interrupted the program on processor selected to execute an I/O interrupt handler program in the operating system to perform I/O interruption services to handle the completion of each group of page transfers. Upon the completion of the interruption handler execution it passed control back to the processor which was interrupted. The result was that the processor which was interrupted due to the asynchronous PAGEIN or PAGEOUT instruction had its efficiency reduced by being diverted to another program (the interrupt handler) during which the processor was not available to execute its primary program.
A synchronous page transfer instruction requires its issuing processor to control all aspects of a page transfer from its initiation until its completion, and does not use any other processor. Unlike an asynchronous page transfer, a synchronous page transfer does not allow its processor to execute any other instructions during the page transfer. A synchronous page transfer instruction does not have any end-of-transfer interruption with its resulting interrupt handler intervention and overhead. The commercial implementations of the PAGEIN/PAGEOUT and MovePage (MVPG) instructions have provided only synchronous page move operations.
The synchronous PAGEIN/PAGEOUT instructions are IBM S/370 supervisory state instructions which use absolute addressing of storage. Often page transfers are used by operating system (OS) software (operating in supervisory state transparent to problem state application programs) to setup problem state programs for execution in MS or to store away execution results of problem state programs in ES.
The prior art of the MovePage (MVPG) instruction is disclosed and claimed in U.S. application Ser. No. 07/424,797 filed Oct. 29, 1989 entitled "Process Using Virtual Addressing in a Non-privileged Instruction to Control the Copying of a Page of Data in or between Multiple Media". The MVPG instruction operates synchronously with its program.
European patent 0 214 670 to Fujitsu discloses synchronous page transfer instructions which have operands dedicated to respective media.